Ewen McKenzie unlocked the secret to Quade Cooper long ago and is again reaping rich rewards as the enigmatic Wallaby playmaker prepares for his 50th Test this weekend. Just 14 months after his rugby career hung by a thread, Cooper will reach his half-century of international caps when he runs out against Wales at Cardiff's Millennium Stadium.

McKenzie says it's no coincidence that Cooper is playing his best Test rugby since his elevation to the Australian vice-captaincy at the start of their European tour. The 25-year-old Queensland first five-eighth has turned himself around on and off the field since labelling the Australian camp a "toxic environment" last September.

He has been a stand-out on the end-of-season tour, mixing his dazzling skills with a composure previously missing from his international resume. McKenzie, who first empowered Cooper at the Reds in 2010, knew what he was getting when he shocked many by promoting him to the national team leadership role.

"I worked out early on… the more responsibility I gave him the better he played, simple as that," he said. "He likes responsibility. A lot of people wouldn't think that but he actually likes the responsibility of running the game plan ... so if you actually back him he'll return the favour."

McKenzie's policy with Cooper has been in contrast to that of predecessor Robbie Deans who gave up on the skilful No.10 after his frustrations about the Wallabies' "boring" play and record against the All Blacks bubbled over. Cooper has since admitted he has matured and learned his lessons to be a better team man, but at the time he claimed the Reds were a more professional outfit.

He was stuck on 38 caps at the time, and struggling in his return from the knee reconstruction he underwent following his forgettable 2011 World Cup campaign, when targeted by the New Zealand crowds. While Deans controversially overlooked Cooper for this year's Lions series, McKenzie also surprised by benching him for his first two Tests in charge, preferring Matt Toomua to play against New Zealand.

But since then, the newly appointed vice-captain has improved with every display to have a major hand in eight of the 13 tries the Wallabies have scored in wins over Italy, Ireland and Scotland. A big part of the Wallabies resurgence has been due to his playmaking and match-winning chemistry with Israel Folau. Cooper put Folau over for one try against Scotland with a perfect inside ball and then combined with the fullback and Stephen Moore for a second to Chris Feauai-Sautia.

Quade Cooper and Israel Folau's on field chemistry contunies to help the Wallabies win